The invention in general relates to an apparatus for producing particles of a foodstuff. Specifically, it relates to foodstuffs having a fat content of at least 50%, a sugar content of not more than 20% and a water content of not more than 10%, with the foodstuff which is present in liquid form being applicable by means of a dosing device in the form of a film or in the form of a strip onto the moved surface of a cooling device with which the foodstuff is at least partly hardenable.
It is generally known in apparatuses for producing chocolate particles to apply the liquid chocolate at a temperature of approximately 30xc2x0 C. to 35xc2x0 C. onto a cooled surface at first in the form of a cooling roller. The application generally occurs in the form of a continuous film with the thickness remaining as even as possible, which thickness can be set with a calibrating roller. The outside jacket of the cooling roller and the outside jacket of the calibrating roller enclose a gap in the thickness of the chocolate film. The passage of a thicker film is prevented by the calibrating roller, which is why it is possible to produce a back-up of the liquid foodstuff, i.e. a bath with a larger depth than the thickness of the later film.
The surface temperature of the cooling roller is at the moment of contact with the liquid chocolate approximately 5xc2x0 C. to 10xc2x0 C. After the first contact of the cooling roller with the chocolate, a crystallization in form of a thin layer occurs at first in the zone of the contact surface. Furthermore, starting from the surface of the chocolate film which is averted from the cooling roller there is also a commencing crystallization after the passage of the calibrating roller as a result of the convective heat transmission to the ambient gaseous medium which occurs there, with the temperature of the gaseous medium being at approximately 10xc2x0 C. to approximately 20xc2x0 C. From the center of the still liquid chocolate film there is a thermal conduction in the direction towards both surfaces, i.e. in the direction towards the cooling roller jacket as well as in the direction towards the gaseous medium encompassing the cooling roller.
The chocolate film leaves the cooling roller in the known method in a state which is crystallized only from the edges, i.e. only in a partial manner, and is therefore placed on the surface of a cooling belt which is led through a cooling tunnel which has a length of approximately 10 to 30 meters. Cold air is guided through the cooling tunnel in a counter-flow, which air has a temperature of approximately 10xc2x0 C. to 15xc2x0 C. The reason for such a complex cooling process is caused by the reasons arising from the special properties that are demanded by high-quality chocolate. A specially desirable crystal structure can only be obtained by cooling with a very low temperature gradient, in which the hardened chocolate shows for the longest possible period the desired gloss and the desired resistance against fat bloom formation.
In the recent past the demand has increasingly arisen in the users of such chocolate particles to also use such particles in aqueous non-frozen media such as yogurts or sweet desserts. In order to avoid problems with microbiology even after a certain storage period of the end product containing the chocolate particles, it is necessary to strive towards the lowest possible number of germs in the chocolate. Since raw cocoa naturally has a relatively high germ infestation, which is harmless per se in the processing into chocolate outside of aqueous non-frozen media, the reduction of germs of the liquid chocolate by pasteurization or sterilization is necessary. The goal of chocolate particles with low germ infestation can only be achieved when a subsequent new infestation with germs can be prevented after the formation of the particles subsequently to a preparational pasteurization or sterilization of the chocolate. In the methods according to the state of the art and the pertinent apparatuses with their considerable constructional sizes, it is hardly possible to ensure low germ infestation or even freedom from germ infestation with economically viable measures. Thus it is not cost effective to perform the entire formation of particles, which also includes the hardening on a cooling roller and a downstream cooling belt, under clean room conditions as is conventionally applied in the pharmaceutical business.
The disadvantage in known particle formation in the forming of a continuous film and its subsequent comminution in the hardened state for achieving the desired particle size is that an exact geometrical shape of the particles cannot be ensured. Particles of a certain size distribution but not precisely one specific size can be achieved for example with the help of a crusher device depending on the chosen crusher tools. Moreover, the efforts relating to design and equipment for successively performed steps in forming a continuous film and in comminuting the hardened film are relatively high.
An alternative method for producing particles of a foodstuff is known from EP 0 976 333 A2 hereby incorporated by reference. Here there is a dripping of liquid foodstuff in a stock of nozzles, whereupon the drops cover a drop path within a drop tower of a height of approximately 10 to 15 m. A cooling gas is guided in a counter-flow to the falling foodstuff particles through the drop tower, with which the hot drops are in a convective heat exchange. At the end of the drop path the foodstuff particles are hardened at least to such an extent that they are no longer plastically deformable when hitting the surface after the occurring acceleration. Depending on the setting of the process parameters (temperature at the stock of nozzles, aperture cross section of nozzles, temperature and speed of cooling gas), it is possible to produce both very evenly formed spherical particles as well as thread-like and ribbon-like particles of irregular length as well as intermediate shapes of the aforementioned types. If the foodstuff is supplied in a sterilized or pasteurized form during the dripping, it is possible to produce sterile or pasteurized particles if the drop tower was also sterilized or pasteurized prior to commencement of the production. The disadvantageous aspect of the known method is on the one hand the relatively low production capacity and on the other hand the high constructional complexity, especially the mandatory large extension in the vertical direction in order to achieve the required cooling periods. Moreover, it is not possible to achieve all the desired particle shapes in the prior art method.
The present invention is based on the object of improving an apparatus of the kind as described above in such a way that the production of foodstuff particles is possible in a cost-effective manner, whereby the change between different particle sizes is to be enabled without any major efforts. Furthermore, the proposed apparatus should allow the production of pasteurized or sterilized particles, which is why the chosen dosing devices must meet the conditions necessary for a reliable and simple pasteurization or sterilization.
Based on an apparatus of the kind mentioned above, this object is achieved in accordance with the invention in such a way that the dosing device comprises an elastically deformable membrane which is in contact with one surface having present the liquid, sterilized or pasteurized foodstuff and which can be deflected in a direction approximately perpendicular to its plane, as a result of which the volume of a conveying chamber for the foodstuff can be changed. Further, the dosing device and the cooling device are disposed in an encapsulated way within an enclosed vessel preferably having a sterilized or pasteurized interior.
Due to the change in volume of the conveying chamber for the foodstuff with the help of the deflection of an elastically deformable membrane, a simple possibility is created to a) precisely dose the quantity of foodstuff passing through the pass-through cross section of the dosing device and b) simultaneously ensure the requirements placed on easy sterilizability and pasteurizability of the apparatus prior to the commencement of production. Because the membrane tightly seals the conveying chamber during its sterilization or pasteurization, sterilization of the conveying chamber of the dosing device can occur with superheated steam or hot air. By using an elastically deformable membrane it is especially possible to omit valve devices with mechanically sealing parts. Especially in the case of a rapid cooling of the liquid foodstuff immediately after leaving the dosing device it is thus possible to prevent the likelihood that highly undesirable deposits occur on the seat surfaces of the valves by undesirable crystallization occurring at an early stage.
A further advantage of the apparatus in accordance with the invention is that it is possible to omit the pass-through of axially movable tappets by limiting the conveying chamber, i.e. the space which comes into contact with the liquid and sterilized or pasteurized foodstuff. Such pass-throughs are particularly critical with respect to the process of sterilization or pasteurization of the apparatus, because there is no defined limit between the sterilized or pasteurized zone and the ambient environment of the apparatus. Each axial stroke movement of such a tappet would move the sterile border from the outside to the inside towards the sterile chamber, thus leading to an uncontrolled conveying process of germs from the ambient environment into the sterile chamber. A membrane, however, leads to a hermetic sealing of the sterilizable or pasteurizable zone. Even in the case of an oscillating conveying movement of the membrane, there will not be any removal of said hermetic sealing of the conveying chamber.
In accordance with an embodiment of the apparatus of the invention, it is provided that the membrane forms a section of the border of the sterilization or pasteurization zone. In this case there are many options for the actuation of the membrane from the surface averted from the sterilization or pasteurization zone. As a result, the membrane can be coupled for example with a tappet which is connected in a non-positive or positive manner or directly with the fabric. There are also many options available for its drive without having to take into account any considerations as to sterilizability or pasteurizability, because said drive is located already completely outside of the border of the sterilization or pasteurization zone.
As an alternative to the aforementioned embodiment it is also possible that the membrane is connected with an actuating tappet on the side which is averted from the foodstuff, which tappet can be guided through the border of the sterilizable or pasteurizable zone by means of a compensator which is hermetically sealed and can be changed elastically in its length. In this case, it is not the membrane per se which forms the border to the sterilizable or pasteurizable zone, so that in the case of damage to it or an incomplete sealing it is not necessary to fear any penetration of germs into the conveying chamber and thus into the liquid foodstuff. This is because the zone which is adjacent to the opposite surface of the membrane is also sterilized or pasteurized.
Preferably, the dosing device comprises at least one nozzle for the outlet of the liquid foodstuff from the conveying chamber. Especially in the production of chocolate particles it is advantageous to provide a strip of capillary nozzles whose outlet diameter is approximately 0.5 mm to 3 mm.
In a further development of the invention it is proposed that the outlet opening of the capillary nozzles is provided with a distance from the moved surface of the cooling device of between 0.5 mm to 10 mm. The cooling device can concern a rotating cooling roller or a moved revolving cooling belt or a succession of the two aforementioned devices. For reasons of minimizing the size of the apparatus, it is preferable to allow the complete hardening of the liquid foodstuff to occur either alone on the cooling roller or alone on the cooling belt. The encapsulation of the entire apparatus as required for production under sterile conditions requires less efforts in this case.
The efforts to ensure the conditions for the continuous production of the sterilized or pasteurized particles can be reduced even further when the temperature of a gas disposed in the interior of the vessel is in the zone of the charging of the liquid foodstuff lower than 0xc2x0 C., preferably lower than xe2x88x9220xc2x0 C., and the temperature of the surface of the cooling device is in the zone of the charging of the liquid foodstuff lower than 0xc2x0 C., preferably lower than xe2x88x9220xc2x0 C. The size and thus also the costs for the encapsulation can thus be reduced considerably by the reduction of the hardening time. Although particles which are hardened under the application of such high temperature gradients do not show the crystal properties which are typical for conventional chocolate, they are still especially suitable for use in an aqueous non-frozen medium, because the criterion of gloss of the particle in the dry state is especially irrelevant. From a taste and sensory point of view such rapidly hardened chocolate particles are perfect.
It is finally proposed in accordance with the invention that a continuously operatable rotary pump is provided for the conveyance of the foodstuff through the conveying chamber and the pass-through cross section of the dosing device. In contrast to reciprocating piston pumps for example, one can omit the use of return valves in rotary pumps in the line section between the pump and the conveying chamber. In the case of a deflection of the membrane into the conveying chamber and thus a reduction of its volume, the thus resulting increase in pressure into the conveying chamber does not allow any return flow of the liquid foodstuff towards the rotary pump, i.e. against the conveying direction, because the rotary pump blocks the cross section of the conveying line completely at all times by means of its conveying member. The increase in pressure into the conveying chamber of the dosing device as a result of the membrane deflection thus always leads to the intended conveyance of the liquid foodstuff through the pass-through cross section of the dosing device, i.e. towards the receiving surface of the cooling device. In this way it is possible to control the interruption or renewed supply of the liquid foodstuff emerging from the dosing device in a very efficient manner.